Can the clustered dark matter and the smooth dark energy arise from the same scalar field?

May, 2002
4 pages
Published in:
  • Phys.Rev.D 66 (2002) 081301
e-Print:
Report number:
  • IUCAA-17-2002

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Abstract:
Cosmological observations suggest the existence of two different kinds of energy densities dominating at small (500 \lesssim 500 Mpc) and large (1000\gtrsim 1000 Mpc) scales. The dark matter component, which dominates at small scales, contributes Ωm0.35\Omega_m \approx 0.35 and has an equation of state p=0p=0 while the dark energy component, which dominates at large scales, contributes ΩV0.65\Omega_V \approx 0.65 and has an equation of state pρp\simeq -\rho. It is usual to postulate wimps for the first component and some form of scalar field or cosmological constant for the second component. We explore the possibility of a scalar field with a Lagrangian L =- V(\phi) \sqrt{1 - \del^i \phi \del_i \phi} acting as {\it both} clustered dark matter and smoother dark energy and having a scale dependent equation of state. This model predicts a relation between the ratio r=ρV/ρDM r = \rho_V/\rho_{\rm DM} of the energy densities of the two dark components and expansion rate nn of the universe (with a(t)tna(t) \propto t^n) in the form n=(2/3)(1+r)n = (2/3) (1+r) . For r2r \approx 2, we get n2n \approx 2 which is consistent with observations.
  • 98.80.Cq
  • 95.35.+d
  • dark matter: cluster
  • dark energy
  • field theory: scalar